A set of chemistry exam scores are normally distributed with a mean of 70 points and a standard deviation
of 5 points.
What proportion of exam scores are between 68 and 73 points?
You may round your answer to four decimal places.
please help

38.117%

Step-by-step explanation:

Firstly, what you do is to calculate the z-score of both points

Mathematically;

z-score = (x-mean)/SD

where mean = 70 and SD = 5

For 68, z-score = (68-70)/5 = -2/5 = -0.4

for 73, z-score = (73-70)/5 = 3/5 = 0.6

The probability we are to calculate ranges from

P(-0.4<z<0.6) = P(z<0.6) - P(z<-0.4)

it is at this point that we make use of z score table

= 0.38117 which is 38.117%

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional

correct answer is b. 27/8

step-by-step explanation: